CVE-1999-0450
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedIn IIS, an attacker could determine a real path using a request for a non-existent URL that would be interpreted by Perl (perl.exe).
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · moderate confidenceIn IIS, an attacker can discover real filesystem paths by sending requests for non-existent URLs that trigger Perl (perl.exe) interpretation. The Perl interpreter reveals path information in error messages, allowing directory structure enumeration.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data= 3.0= 4.0= 2.0= 5.0CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Authentication
- None
- Confidentiality
- Partial
- Integrity
- Partial
- Availability
- Partial
AV:N/AC:L/Au:N/C:P/I:P/A:P
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Confirm IIS/IIS versionOpen IIS Manager or run 'iisweb.vbs /query' (IIS 6) or check HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W3SVC\Parameters in the registry for the version valueAffected if The installed version is 2.0, 3.0, 4.0, or 5.0 (IIS 2.0-5.0 are affected)
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Locate perl.exe in web-accessible directoriesSearch for perl.exe in common CGI directories such as /scripts, /cgi-bin, /inetpub/scripts, or the web root. Check via file system or command: 'dir /s /b C:\perl.exe' or 'where perl.exe'Affected if perl.exe exists in any directory accessible via HTTP requests
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Verify .pl script mapping is enabledIn IIS Manager, under 'Home Directory' or 'Configuration' > 'App Mappings', verify that .pl extension is mapped to perl.exe (typically C:\perl\bin\perl.exe %s %s)Affected if The .pl extension is mapped and enabled as a script mapping
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Test for path disclosure via Perl errorSend an HTTP request to the server for a non-existent .pl file, for example: GET /nonexistent.pl HTTP/1.1. Examine the error response for full filesystem path informationAffected if The error message returned contains absolute Windows filesystem paths (such as C:\inetpub\... or similar)
A user is affected if their IIS version is 2.0-5.0 AND perl.exe is accessible via the web AND requesting a non-existent .pl file returns absolute filesystem paths in the error response.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor dataDisable or properly secure perl.exe in IIS, configure custom error pages to avoid revealing server path information, and ensure CGI interpreters do not expose filesystem paths in error responses.
- Consultation2.0 h
- Implementation3.0 h
- Testing2.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-1999-0450 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-1999-0450 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
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